Patent Literature 1 describes a technique of bringing a probe into contact with a semiconductor device and measuring the electrical characteristics thereof, in order to detect defects in the wiring lines of the semiconductor device. In order to precisely measure the electrical characteristics of the semiconductor device, the probe has to be brought into contact with a predetermined position of the semiconductor device. Hence, SEM images based on a scanning electron microscope (SEM) are used.
In recent years, there has been a progress in the miniaturization of the wiring pattern of a semiconductor device, as seen in 30 nm and 20 nm devices. For example, contacts of a transistor cannot be observed in the most-advanced semiconductor device unless a magnification of 20,000 to 30,000 is applied. Accordingly, there is the need for high-magnification, high-resolution SEM images.
In order to increase the magnification and resolution of SEM images, electron optical conditions (acceleration voltage, emission current, and the like of an electron beam) need to be changed. If the electron optical conditions are changed, however, a sample may suffer damage, thus affecting the electrical characteristics of a semiconductor device. Accordingly, in addition to increasing the magnification and resolution of SEM images, it is essential to avoid affecting the electrical characteristics of the semiconductor device. These two objectives are in a trade-off relationship, however.
In a step of bringing a probe into contact with a semiconductor device (probe needle contact), information on the current position of the probe needs to be acquired. That is, the real-time property of an SEM image is required.